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Removing vestigal flattens in coastal areas

I recently created photo scenery for an area of coastline that has numerous fiords extending into mountains. I overlayed my photoscenery over a 38m terrain mesh, and created precise watermasks for the fiords using alpha channel bitmaps. Everything compiled fine, and the photos fit the mesh perfectly, with my coastline pretty much where the mesh went from steep to flat.

Anyway, the fly in the ointment was that even though the old coastlines are gone, their flattens remain, often cutting straight through mountains, and leaving weird flat areas everywhere.

Can these vestiges be removed easily, ie with a single large exclude? I don't need any water related flattens anywhere near my scenery. Is this possible with sbuilder or another program?

If this is addressed somewhere else in the forums, please direct me.



Staff member
Resource contributor
Hi sstobbe.

This is a characteristic of fs2002 and fs2004. you cannot exclude a flatten. It is fixed in FSX.

The solution is to find the relevant, default HP file and replace it with an altered version that is decompiled-recompiled to exclude the water in the area of your scenery. Admittedly, not a good solution.

Thanks, Dick. Couple other question for you or others:
Is there an easy way to identify the offending HP files? Does the HP file nomenclature include location information?
Also, can I just eliminate the HP files? I have created the new coastlines and fiords through an alpha channel watermask, so wouldn't these replace the old ones completely?



Resource contributor

The following is an extract of the Help file from Sbuilder 205:

Regards, Luis

In order to append a LWM BGL file to a project you only need to point to the filename and the folder where it is located. The specified BGL file must contain valid LWM data. You can either append files produced by you (with SBuilder or other) or default LWM BGL files. Default LWM files for Western Europe, for example, are located in the folder:

C:\Program Files\Microsoft Games\Flight Simulator 9\Scenery\Eurw\Scenery

Different regions of the world will be located in different folders like \Eure\ for Eastern Europe, \Afri\ for Africa, \Name\ for North America (East part) and so on.

Inside these folders you have several files. The following files are LWM files:

FL9XXYY0.BGL - these files refer to flatten polygons
HP9XXYY0.BGL - these files refer to hydro polygons (and/or hydro area fills)
All LWM files cover a complete LOD5 square. The XX and YY appearing in the filename refer to the X and Y coordinates of the LOD5 square to which the file refers to. In order to know which file applies for a given location you look to the LOD5 coordinates that appear in the status bar when you have the mouse in the desired position. In the south of Portugal, for example, the satusus bar shows LOD5 45 18. Therefore if you want to load the hydro LWM data for that region you look for the file HP945180.BGL. Note that there is a leading 9 and a trailing 0 in the sequence of digits that define the location.
Ok, fixed my problem, albeit in a rather heavyhanded way.

I identified the offending .cvx files using the .tmf viewer that comes with the fsx sdk, and simply nuked them all by changing their extensions! Wow, that felt good. The flattens are now gone.

My scenery already has its own watermask which extends well out to sea, and good photoscenery, so I really could care less about fsx roads, powerlines, parks, and other junk possibly contained in the cxv's.

Thanks for the great suggestions. I really found the "Terrain Design for Flight Simulator X" , available by searching forums on Avsim. It explains core concepts, in addition to methods.